Listeria monocytogenes in rhombencephalitis - lineage I

Listeria (L.) monocytogenes is a genetically diverse and opportunistic pathogen causing life-threatening infections in diverse mammalian species including humans and ruminants. As little is known of the association of strains with clinicopathological phenotypes, we used ruminant-associated L. monocytogenes isolates from well-defined cases of clinical infections and the environment as a model to study potential strain-associated virulence and organ tropism. The phylogeny of isolates and their virulence-associated genes were analyzed by multilocus sequence typing (MLST) and genome sequence analysis. Additionally, a panel of representative isolates was subjected to in vitro infection assays. Our data suggest the environmental exposure of ruminants to a broad range of strains and yet the strong association of sequence type (ST) 1 from clonal complex (CC) 1 with rhombencephalitis, suggesting increased neurotropism of ST1 in ruminants, which is possibly related to its hypervirulence. This study emphasizes the importance of considering STs in surveillance, epidemiological investigation and disease control of L. monocytogenes.